VERTICAL SITUATION DISPLAY - Boeing: The Boeing … · Boeing has developed a vertical situation display to help prevent controlled flight into terrain and approach and landing accidents

Boeing has developed a vertical situation display to help prevent controlled flight intoterrain and approach and landing accidents.In addition, the vertical situation display isdesigned to reduce airline operating costs bydecreasing the number of missed approaches,tail strikes, and hard landings and by reducingvertical navigation training time.

3AERO 3AERONo. 20, October 2002

TECHNOLOGY/PRODUCT DEVELOPMENT

VERTICALSITUATIONDISPLAYfor IMPROVED FLIGHT SAFETY

and REDUCEDOPERATING

COSTS

DAVID CARBAUGH

CHIEF PILOT

FLIGHT OPERATIONS SAFETY

BOEING COMMERCIAL AIRPLANES

SHERWIN CHEN

ENGINEER

FLIGHT DECK ENGINEERING


ALAN JACOBSEN

TECHNICAL FELLOW



ROBERT MYERS

MANAGER



JOHN WIEDEMANN

ASSOCIATE TECHNICAL FELLOW



4 AERO No. 20, October 2002

elements common across all

Boeing models and can be imple-

mented within the constraints

of available space on existing

airplane displays.

The VSD will be offered by

early 2003 as a customer option on

in-production 737s and by retrofit

on 737-600/-700/-800/-900 airplanes

already in service. Implementation

of the system on other Boeing

models is under consideration.

The value of the VSD can

best be understood through a

discussion of the following:

1. Current method for assessing

vertical situation.

2. Development of the VSD.

3. Display features.

4. Benefits of the VSD.

5. Implementation on Boeing

airplanes.

CURRENT METHOD FOR ASSESSING VERTICAL SITUATION

Currently, flight crews must assimilatevertical situation information from various sources to create a mental picture of the vertical profile. Thesesources include barometric and radioaltitude readouts, the vertical speedindicator, ground proximity warningsystems, terrain depiction systems, andnavigation information from the flightmanagement computer (FMC) and navigation charts. Flight crews usuallyare very effective at integrating thisinformation. However, they can be hard-pressed to formulate and maintaina completely accurate mental model of the vertical profile, especially during time-critical or high-workload

situations or during initial training using vertical navigation (VNAV) systems. This makes misinterpretationof the vertical situation more likely.

During the past several years,various options have been investigatedto provide vertical situation informa-tion on the flight deck. Although manynew technologies promise to deliverimproved overall situation awareness,significantly enhancing the safety of the worldwide commercial airplane fleet will require cost-effective solu-tions that are relatively easy to retrofit.Presenting flight crews with a sideview of the vertical dimension is onesuch solution — it targets a significantpart of the problem yet involves only minor changes to the airplane and airline infrastructure.

DEVELOPMENT OF THE VSD

Boeing evaluated various methods ofimproving vertical situation awarenesswith the goal of reducing the overallaccident rate of the commercial airtransport industry. Because the measure-ment of vertical awareness is subjectiveand there is no one-to-one correlationbetween vertical awareness and accident prevention, Boeing decidedthat measurements of vertical situationawareness alone are insufficient forevaluating the safety of various tech-nologies. Instead, databases — such asthose of airline incident reports andaccident reports for the past 10 years —were used as one source of evaluationcriteria. The incident reports were used to guide the direction of conceptdevelopment, whereas the accidentreports were used to determine theexpected effect of specific concepts on the accident rate.

In addition, flight crews flew threetypes of scenarios in an engineeringflight deck simulator that reflected thetarget accident types (i.e., CFIT andapproach and landing). The scenariosinvolved an approach during which the

f the more than 200 heavy

air transport accidents involving

hull loss or fatalities in the past

10 years, more than 50 percent

were associated with either con-

trolled flight into terrain (CFIT)

or the approach and landing

phases of flight (fig. 1). Many of

these accidents involved inade-

quate or loss of vertical situation

awareness by flight crews.

To help prevent CFIT and

approach and landing accidents,

Boeing has created a clear graphi-

cal picture of the airplane ver-

tical flight path that enhances the

flight crews’ overall situation

awareness. This vertical situation

display (VSD) works in conjunc-

tion with the terrain-mapping

feature of the terrain awareness

and warning system (TAWS)

(e.g., the Honeywell enhanced

ground proximity warning system)

to provide flight crews with an

intuitive presentation of the

vertical situation relative to the

surrounding terrain and the final

approach descent path. In addi-

tion to terrain alerting, the TAWS

provides a lateral, or top-down,

view of terrain. The VSD depicts

a profile, or side view, of terrain

and flight path data.

The VSD is designed to

maximize safety while mini-

mizing required changes to air-

plane hardware and airline flight

operations and training. It also

capitalizes on airplane design

O

1

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5AERONo. 20, October 2002

airplane must descend later than normalto intercept the glideslope, an approachwith a steep glideslope, and level flighttoward mountainous terrain. Flight crewperformance, subjective ratings, andobservations were gathered.

Results showed that the VSD wasthe most effective display format in all three scenarios. The least effectivedisplay was a simple three-dimensional(3D) perspective display. The VSDscored high in the areas of early threatrecognition, effectiveness when flying

steep approaches, and maintenance of a stabilized path.

Based on these results, Boeing choseto pursue further development of theVSD as the most effective and practicaloption that could be implemented in thenear term. This decision was not meantto preclude further developments in 3D perspective displays.

Developing a side-view vertical profile display necessitated refinement of the human interface requirements.Boeing worked with airlines, suppliers,

and regulators to ensure efficient devel-opment and implementation as well asthe establishment and support of an in-dustry standards team. Human interfacerequirements were refined in the 737engineering flight deck simulator be-cause the 737 uses various display typesand sizes. Boeing wanted to ensure thatany VSD design could be implementedon the many sizes of electronic displaysused today, including the larger ARINCD-size (8- by 8-in) and the smallerARINC B-size (6- by 7-in) displays.

HEAVY AIR TRANSPORT ACCIDENTS INVOLVING FATALITIES AND/OR HULL LOSS

FIGURE

1


DISPLAY FEATURES

A VSD graphically represents a viewof the vertical profile of the airplane.The Boeing VSD depicts a swath thatfollows the current track of the airplaneand therefore is referred to as a track-type VSD. When selected by the flightcrew, it appears at the bottom of thenavigation display (fig. 2).

Figure 3 shows an example of theBoeing side-looking VSD. The basicfeatures of this VSD include altitudereference and horizontal distancescales, an airplane symbol, a verticalflight path vector, terrain depiction,navigation aids, glideslope depiction,and various information selected by theflight crews and FMC such as themode control panel (MCP)–selectedaltitude, minimum decision altitude,and selected vertical speed predictor.

The development of the VSD formatinvolved a thorough human-centereddesign approach. All the features had to meet basic flight deck philosophies

and design guidelines. In addition,because clutter always is a concern,each feature was added only after itwas shown to provide a significantbenefit in terms of enhancing flightcrew awareness. Some of thesehuman-centered design requirementsincluded the following:

■ Information had to be consistentwith that which already appears onother flight displays.

■ Information had to be intuitive andfollow standard flight informationsystem and navigation display conventions.

■ The display had to use existingsymbols to as great a degree aspractical.

One issue identified with the track-type VSD was that flight crewswanted additional terrain look-aheadin the direction of a turn. An algorithmwas invented that expands the swath inthe direction of the turn to give flightcrews the desired result.

One guiding philosophy was thatthe VSD must be intuitive. The swathwidth actually is dynamic and variesas a function of navigation accuracyrequirements and whether or not theairplane is turning. Consequently,the swath is depicted on the lateraldisplay simply with two dashed lines.The information contained betweenthese two lines on the lateral view isthe information depicted on the VSD.This results in a display that is moreintuitive to flight crews.

Wherever appropriate, symbolsfrom other displays were incorporatedinto the VSD. For example, the symbol for MCP-selected altitude isthe same shape as the corresponding symbol on the primary flight displayaltimeter tape.

Although the VSD can be used to assess path stability, path stabilityis only part of the equation for a stable approach. The other factor isspeed stability. To facilitate speed stability, a new symbol was introducedon the VSD. The range-to-target

VSD LOCATION ON FLIGHT DECK

FIGURE

2

3


crews as they establish the glide path.Terrain alerting from the TAWS is disabled gradually during this phase of flight to eliminate nuisance alerts,but the VSD is available full time.

The VSD also complements theincreased use of constant-angle, areanavigation, and required navigationperformance (RNP) approaches byproviding immediate validation of theselected approach path and allowingfull-time monitoring of the airplaneposition relative to the selected glidepath. As low-altitude, in-cloud maneuvering becomes commonplaceand RNP criteria allow better utiliza-tion of restricted airspace, the VSDwill serve as an invaluable confirma-tion of airplane performance.

The VSD will provide additionaloperational benefits. Earlier recogni-tion of terrain clearance problemsfacilitates more timely go-arounds andearlier CFIT avoidance. In addition,with improvements in vertical aware-ness, flight crews have an improved

speed symbol is a green dot thatshows where excess speed will bedissipated along the vertical flightpath vector. If excess speed is not anissue, then the symbol will notappear on the display.

The display remains stable duringdynamic conditions. Flight crewsshould keep in mind that the VSD isa supplementary display and as suchis not intended for use as the primaryreference during dynamic maneuversand procedures.

Incorporating the VSD does notrequire any changes to flight opera-tions procedures, except for the addition of procedures that apply tothe VSD in non-normal conditions.Additions to the airplane flight man-ual describe the features of the VSD.Flight crew training regarding theVSD only involves written materials.

BENEFITS OF THE VSD

The main benefit of the VSD isimproved safety. The VSD will giveflight crews an intuitive view of thevertical situation just as the currentmap display provides an intuitivedepiction of the lateral situation. In conjunction with the other safety features of the flight deck, this in-creased vertical situation awarenesshelps prevent CFIT and approach and landing accidents and incidents,thereby further decreasing the alreadylow accident rate of the worldwidecommercial airplane fleet.

The VSD depicts terrain informa-tion from the TAWS or other onboardsources from another perspective.The TAWS generates a lateral viewof the surrounding terrain and pro-vides terrain proximity alerting. TheVSD depicts the vertical dimensionof the terrain (fig. 4), which willallow crews to recognize possible terrain conflicts more readily, beforea TAWS alert is generated.

The VSD also depicts the finalapproach segment of the intendedpath of the airplane to the runway(fig. 5), thereby assisting flight

ability to monitor the vertical path.Earlier recognition of unstabilizedapproaches helps reduce the numberof go-arounds and missed approaches.Because many unstabilized approachproblems are manifested during thelanding phase of flight, earlier recog-nition also should reduce the numberof hard landings, runway overruns,brake fires, and tire failures. This will help reduce airline operatingcosts by extending the life of the air-frame structure, landing gear system,tires, and brakes and by reducing the airplane maintenance downtimeassociated with landing problems.

Finally, the intuitive nature of the VSD will allow flight crews toassess the vertical situation quickly,thus reducing overall workload.Crews will have more time during the most critical phases of flight —climb, descent, and final approach —to focus on other routine tasks and handle any unusual circumstancesthey may encounter.

4

EXAMPLE OF A SIDE-LOOKING VSD

FIGURE

3


IMPLEMENTATION ON BOEING AIRPLANES

The VSD has only recently become a viable option for increasing vertical situation awareness. Three factors precluded an earlier introduction of the technology. The information pre-sented on the VSD must be accurate.Accuracy requires a good terrain data-base, and that technology has become

available only recently for commercialapplications.

Second, flight crews must have con-fidence in the accuracy of the positionof the airplane relative to physical features. Although most navigation systems are very reliable and robust,the advent of the global positioning system has improved lateral and ver-tical accuracy of the airplane position.

Finally, as a result of improve-ments in display technology and com-putational throughput, the quantity of display symbols is not as limited as it once was.

The VSD was designed for incorpor-ation within the constraints of currentproduction models. Implementation onin-production airplanes requires systemchanges to the avionics displays,

5

AIRPLANE HEADING INTO TERRAIN BEFORE A CAUTION TERRAIN ALERT IS GENERATED

FIGURE

4


FMC, and TAWS. For the avionics displays, thedisplay system softwaremust be updated. TheFMC requires a softwareup-grade, and new hard-ware and software arerequired for the TAWS.In-service airplanes mayrequire additional hard-ware upgrades to allowfull implementation.

The introduction of new, large liquid crystaldisplay screens on Boeingairplanes facilitates imple-mentation of the VSD. TheVSD also was designed tobe compatible with cathoderay tube–based flightdecks. Although Boeinghas focused on integratingthe VSD into the flight deck, a largeportion of the worldwide fleet in the

next 5 to 10 years still will useelectromechanical instrument flight

decks. The VSD can beimplemented on these flightdecks as a stand-alone dis-play system. These retrofitsolutions are in development.

Boeing has developed the VSD so that additionalfeatures can be added. Oneexample is the depiction of the vertical profile alongthe entire planned flight path. Showing the verticalswath along the plannedflight path of the airplane,instead of just along the current track, provides several benefits. Not onlymay this enhance awarenessof the vertical mode, butVNAV and lateral naviga-tion concepts also may besimplified for training. Other

envisioned enhancements include pro-viding weather and traffic information.

S U M M A R YThe VSD is another step on the evolutionary path of flight deck displays. The display is a natural complement to and outgrowth of the lateral moving map introduced into commercial fleets in the 1970s and 1980s.The VSD can have a significant and beneficial effect on commercial air transport safety. By presenting the flight crew with a simple graphicalpicture of the vertical dimension, vertical situation awareness isenhanced, which potentially can significantly reduce the number of airtransport accidents in the worldwide fleet in a realistic time frame. TheVSD can be implemented without major airplane hardware changes. The system will be offered by early 2003 as a customer option on in-production 737s and by retrofit on 737-600/-700/-800/-900 airplanesalready in service. Implementation of the system on other Boeing modelsis under consideration.

FINAL APPROACH AND RUNWAY

FIGURE

5



Next-Generation 737 Flight Deck with VSD.

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VERTICAL SITUATION DISPLAY - Boeing: The Boeing … · Boeing has developed a vertical situation display to help prevent controlled flight into terrain and approach and landing accidents